Hydrometallurgical treatment of metal-bearing materials, such as metal ores, metal-bearing concentrates, and other metal-bearing substances, has been well established for many years. Moreover, leaching of metal-bearing materials is a fundamental process utilized to extract metal value from metal-bearing materials. Typical leach processes comprise contacting a metal-bearing material with an aqueous solution containing a leaching agent which extracts the metal or metals from the metal-bearing material into solution. For example, in copper leaching operations, especially copper from copper minerals, such as chalcopyrite and chalcocite, aqueous sulfuric acid is contacted with a copper-bearing ore. During the leaching process, acid in the leach solution may be consumed and various soluble components are dissolved thereby increasing the metal content of the aqueous solution.
The aqueous leach solution containing the leached metal can then be treated by, for example, solution extraction, wherein the aqueous leach solution is contacted with an organic solution comprising a metal-specific extraction reagent, for example, an aldoxime and/or ketoxime, to form an aqueous phase and an organic phase. The metal-specific extraction reagent extracts the metal from the aqueous phase into the organic phase. During a solution extraction process for copper and certain other metals, a leaching agent may be regenerated in the aqueous phase. For example, when sulfuric acid is used as the leaching agent, sulfuric acid can be regenerated in the aqueous phase when copper is extracted into the organic phase by the extraction reagent.
After copper is removed from the aqueous phase into the organic phase, the diluted aqueous solution, now called the raffinate, may be recycled back to the leaching process, recycled to the front of a solid-liquid separation process, and/or forwarded to secondary metal extraction processes, such as, for example, cobalt recovery.
Numerous technical challenges exist with typical leaching and solvent extraction processes. For example, under current leaching and solution extraction processes, large concentrations of soluble metal and metal precipitate can be lost in the metal-depleted, acid-containing aqueous phase raffinate solutions. These losses lead to inefficiencies and relatively low overall process yields. Additionally, relatively high primary metal concentrations (such as copper) in the raffinate make recovery of secondary metals costly and possibly impractical.
Accordingly, systems and methods for more easily controlling process conditions, such as the concentration of a primary metal the raffinate solution, would be advantageous. Additionally, systems and methods for improved recovery of secondary metals from a raffinate solution are desirable.